Apparatus for truing grinding and abrasive wheels



E. A. COOKE March 11; 1941.

APPARATUS FOR TRUING GRINDING AND ABRASIVE WHEELS Filed A ril 10. 19:9

'7' Sheets-Sheet :1

Mm h, 19 1. E. A; CO KE APPARATUS FOR TRUING GRINDING AND ABRASIVE WHEELS Filed April 10; 1939 7 Sheets-Sheet 2 March 11, 1941. coo 2,234,539

APPARATUS FOR mums eamnme 1mm musxva WHEELS Filed April 10, 19:9 7 sheets-sheet s March 11, 1941. CQOKE I 2,234,539

APPARATUS FOR TRUING GRINDiNG AND ABRASIVE WHEELS Filed April 10, 1939 1 v Sheets-Sheet 4 March 11, 1941- E. A. COOKE 2,234,539

APPARATUS FOR TRUING GRINDING AND ABR ASIVE WHEELS Filed April 10, 19:9 7 Sheets-Sheet s ullllllllh E. A. COOKE March 11, 1941.

APPARATUS FOR TRUING GRINDING AND ABRASI VE WHEELS Filed April 10, 1939 '7 Sheets-Sheet 6 F/a. /a.

Mafch 11, 1941. E. A. COOKE 2,234,539

I APPARATUS FOR 'rxume enmnme AND ABRASIVB WHEELS 'Filed A ril 10, .1939 Y, 'r Sheets-Shet 'r Patented Mar. 11, 1941 UNITED STATES EXAMINER PATENT OFFICE APPARATUS FOR TRUING GRINDING AN'D ABRASIVE WHEELS pany of Great Britain Application April 10, 1939, Serial No. 266,950 In Great Britain April 11, 1938 16 Claims.

This invention relates to apparatus for truing grinding and abrasive wheels and the like, for example in grinding and abrading machines.

An object of the invention is to provide a truing unit. including a primary link turning about a primary axis and a secondary link turning about a secondary axis on the primary link and carrying a diamond or the like and also a follower which cooperates with a guide or fence arranged in accordance with the form desired for the operative part of the grinding or abrasive wheel.

A further object is to provide straight-line truing by so determining the effective lengths of the links and the arrangement of the guide or fence that when the links are swung about their pivots with the follower in engagement with the guide or fence the diamond or the like is caused to move along a straight-line path. To this end, the distance between.the diamond and the secondary axis may normally be equal to the distance between the secondary axis and the follower and also equal to the distance between the primary and secondary axes, the guide or fence being so arranged that the follower in engagement therewith moves radially with respect to the primary axis.

Yet a further object is to provide for adjustment of the diamond or like truing device on the secondary link so as to adjust the distance between the diamond and the primary axis when it is desired to true a curved surface and, for this purpose, means may be provided for looking the primary and secondary links together so that they can turn as a unit about the primary axis.

The frequency with which the grinding wheel of a grinding or abrading machine requires dressing or truing depends upon various factors, for example the coarseness of the abrasive grain, the type of bond employed and the material ground. In most instances the grinding wheel requires truing se'"eral times for each article dealt with and it is therefore desirable to avoid the necessity for removing the work from the work support, e. g. a pantograph which serves to locate the work and template or copy, and substituting the truing device on every occasion when truing is necessary. A further object of the invention is to overcome this difliculty by mounting the main supporting arm for the truing unit on the grinding machine in such a manner that the truing unit can be swung at will into or out of its operative position. In this way the work can be removed from the operative position and the truing unit swung into the operative position on each occasion when truing of the grinding wheel is necessary.

Yet another object of the invention is to obviate the necessity for disturbing the work before truing can be efiected by mounting the truing unit directly on a fixed part of the machine, means being provided for adjusting the unit on the said fixed part towards and away from the grinding wheel so that the truing unit lies adjacent to a part of the grinding wheel remote from the work support and truing can be efiected without moving the work support or table out of its operative position. Another object of the invention is to provide the truing unit with its own microscope, at least part of the optical system of the microscope being conveniently housed within the pivot of the primary link, the said pivot being hollow for this purpose.

A truing unit according to the invention may be employed in conjunction with engraving machines such as that described in the specification of the United States patent application Serial No. 151,516, and some practical arrangements according to the invention are shown, somewhat diagrammatically and by way of example, in the accompanying drawings, in which- Figure 1 is a plan showing one form of truing unit mounted on the machine, the truing unit being shown in its inoperative position,

Figure 2 shows the truing unit in plan and on an enlarged scale, the truing unit being in its operative position,

Figure 3 is a side elevation in the direction of the arrow X in Figure 2,

Figure 4 represents the graticule of the microscope included in Figure 3,

Figure 5 is a section on the line VV of Figure 2,

Figures 6, 7 and 8 illustrate diagrammatically the operation of the truing unit when employed for truing a V-edge of a grinding wheel,

Figures 9, 10, 11, 12 and 13 are similar diagrams illustrating the operation when truing five further forms of grinding wheel,

Figures 14 and 15 show, in plan and side elevation respectively, the mechanism for adjusting the truing unit transversely to the plane of the grinding wheel,

Figures 16, 1'7, 18 and 19 illustrate, by way of example, five forms of grinding wheel in the truing of which the truing unit is adjusted transversely as described with reference to Figures 14 and 15,

Figure 20 shows, in side elevation, another arrangement according to the invention,

Figure 21 is a plan of yet a further arrangement of the truing unit,

Figure 22 is an exploded view of linkage included in Figs. 1 to 5, 14, 15 and 20.

In the arrangement shown in Figure 1 the machine comprises a fixed base A from which projects brackets A to carry pivot bearings for a pantograph A having an associated work table A copy table A and tracer support A The tool, in the example illustrated, is shown as a grinding wheel B carried on a horizontal shaft B which is mounted parallel to the primary plane A and is driven by an electric motor (not shown) mounted on a facing 13 of a casing B The casing B is carried on the head of a plunger which can reciprocate up and down in a cylinder forming part of a cross-slide B The cross-slide B can be adjusted on a slideway B in a direction at right angles to the primary plane A by means of a handwheel B The work table A can be moved into and out of the working position shown by swinging the pantograph A about the brackets A The machine thus far described corresponds to that described in the specification of the said patent application Serial No. 151,516.

A work microscope A is mounted on a fixed bracket A and a copy microscope A is carried on a slide A A truing unit generally indicated at C is carried by a supporting arm C mounted on a pivot C carried by the hood B of the grinding wheel B. The arm C can thus be swung about the pivot C either to bring the truing unit C into an operative position with respect to the grinding wheel B as shown in Figures 2, 3 and 5, or to swing the truing unit C clear of the grinding wheel B as shown in Figure 1 thus permitting the work table A to be moved into the operative position with respect to the grinding wheel B. In this way the truing unit C can be made wholly independent of the work support and truing can be carried out as and when required by merely moving the work out of the operative position and swinging the truing unit C into the operative position.

As shown in Figures 2, 3 and 5 the truing unit comprises a primary link D mounted to pivot on a primary spindle C (Figure 5) journalled in a bracket C carried by the arm C the axis E of the spindle C constituting a primary axis which, when the truing unit C is in its operative position, lies in or parallel to the working plane A of the machine. A secondary link D is mounted to pivot about a secondary axis E on the primary link D The secondary link D is furnished with a follower F which will cooperate with either of two fences F -shown in Figures 1 and 2, the arrangement being such that when the links D D are swung about the primary axis E so that the follower F engages one of the fences F and the links are moved so that the follower F moves along the fence F the secondary link D which carries a holder D for a pointed diamond D or the like, moves. so that the point of the diamond D moves along a straight-line path as hereinafter described. This movement corresponds to that usually referred to as the "Scott-Russel straight-line movement.

The secondary link D carries a guide D for supporting the diamond holder D which guide is mounted to pivot about the axis D preferably coincident with the follower F, so that the diamond D can be angularly adjusted within narrow limits about the axis D by means of adjusting screws D The diamond holder D can also be translationally adjusted on the guide D by means of a screwthreaded spindle D secured to the holder D and in screwthreaded engagement with a micrometer nut D journalled in a lug formed integral with the guide D. The micrometer nut D carries or cooperates with a Vernier scale to indicate the position of adjustment of the holder D relatively to the primary axis E The diamond D can also be adjusted relatively to the holder D by means of a knurled head D in screwthreaded engagement with the holder. The secondary link D carries a strip carrying a sighting device D for assisting the operator in positioning the primary axis E so as to lie accurately in the working plane A Though the use of the micrometer nut D and micrometer screw, or a graduated wedge, as referred to above are useful means for determining the adjustments of the diamond D, it is preferred to employ the microscope A for this purpose. To this end the microscope A has a graticule as shown in Figure 4, comprising three angles A say, 47.5", and 60 respectively for the purpose hereinafter described, and two scales A and A for measuring the displacement of the diamond D in two directions at right angles to each other, the scale A being employed for determining the diamond adjustment effected by the nuts D and D The primary link D has an extension F furnished with a knob F and the secondary link D has knobs F for facilitating manual operation of the links about their axes. The secondary link D also has a notch or recess for engagement by a latching stud F carried by the extension F of the primary link D, the latching stud when engaged, as shown in Figures 3 and 5, locking the primary and secondary links D D together so that they are constrained to swing as a unit about the primary axis E The bracket C mounted to slide on the arm C is adjustable along this arm by operation of a knurled head C which rotates a spindle C in screwthreaded engagement with the bracket. Positioning of the truing unit C with respect to the microscope A whose optical axis lies in the working plane A", is obtained by means of an adjustment screw C" (Figure 2) carried by the arm C and cooperating with an abutment C on the fixed frame of the machine, a clamp C provided on the arm C cooperating with a slot C in a fixed plate for locking the arm C in the position of adjustment, i. e. whether the unit C is in the operative or inoperative position.

The bracket C is furnished with a dovetailed slot F accurately machined on a radius struck from the primary axis E and extending through 180 and engaged by two blocks F each carrying a fence F Each block F" can be adjusted along the slot F and locked in the position of adjustment by a stud F which bears against the bracket 0. Each fence F is locked in position on the associated block by a stud F so that when this stud is released the fence F can be adjusted towards or away from the primary axis E The arrangement is such that the follower F, when moved along either fence, will traverse a path radial with respect to the primary axis E The inner end of each fence is provided with a flange or projection which serves to limit the movement of the follower F towards the primary axis E The follower F can be brought into engagement with either of the fences F according to which side of the edge of the grinding wheel B is to be trued.

Assuming, therefore, that it is desired to true the operative edge of a grinding wheel as shown in Figure 6, the pantograph A is swung out about the pivots A so that the work table A lies clear of the working plane A Having released the clamp C the arm C is swung from the position shown in Figure 1 to that shown in Figures 2, 3 and 5, the bracket C being adjusted along the supporting arm C until the sighting piece D is brought into coincidence with the apex of the desired angle A on the graticule of the microscope A The primary axis E is thus set accurately in the working plane A. The arm C is now locked in this position of adjustment by tightening the clamp C. In order to bring the most prominent point of the diamond D into coincidence with the primary axis E the studs D are adjusted so as to swing the diamond holder about the axis D as may be required. The distance between the diamond D and the secondary axis E is now equal to the distance between this secondary axis and the axis D of the follower F, and also equal to the distance between the secondary axis E and the primary axis E By grasping the handles F and swinging the primary and secondary links to one side of the plane of the grinding wheel B, for example to the right as diagrammatically shown in Figure 6, the follower F is brought to bear against the fence F which has previously been adjusted along the slot F in accordance with the desired angle of the operative edge of the grinding wheel B, e. g. 475, 50 or 60 according to the angle A selected. The secondary link D is now moved so as to cause the follower F to move to and fro along the fence F the path of movement of the diamond D, which is observed through the microscope A, being along a straight line corresponding to one limb of the angle A selected on the microscope graticule. Any adjustment necessary to bring the point of the diamond D accurately on to the graticule of the microscope A is effected by adjusting the fence F along the guide slot F and then looking the fence in position by means of the stud F The diamond D is fed towards the grinding wheel B by'adjusting the bracket C along the arm C by means of the knurled head the follower F moving radially with respect to the primary axis E whereas the diamond point moves along a straight line so as to true one face of the V-edge of the grinding wheel as shown in Figure 6. The follower F is now moved from the fence F on one side of the plane of the grinding wheel B and is swung over into engagement with the other fence (which has been omitted from Figure 2 for the sake of clarity but is adjusted in accordance with the angle of the grinding wheel as above described), he process being repeated on this side of the grinding wheel to true the other face of the V-edge thereof.

Having thus trued the angle at the edge of the grinding wheel B the edge is rounded to the required radius as follows. The follower F is brought into the central position shown in Figure 2 and diagrammatically shown in Figure 7 and the latching stud F is engaged in the recess in the secondary link D The diamond D is now moved away from the primary axis E as shown in Figure 7, by adjusting the diamond holder D on the secondary link by means of the knurled nut D this movement which is precisely determined by means of the scale A on the microscope A",

being equal to the radius required for the operative edge of the grinding wheel B. With the grinding wheel in rotation the links D D are oscillated to and fro and the bracket C carrying the primary and secondary links is fed along the arm C by means of the knurled head C in a direction towards the grinding wheel B. The diamond D is thus moved to and fro along a circular arc (Figure 8) the two fences limiting the angle of swing, until the primary axis E lies in the position E shown in Figure 7 so that the point of the diamond D lies at a distance from the point E equal to the radius to be produced on the grinding wheel.

The truing of the grinding wheel 13 is now complete and the clamp C is released so as to release the arm C which can be swung away until the truing unit C is removed from the working position, the supporting arm C being then relocked by means of the clamp C The operative edge of the grinding wheel B is next brought into the working plane A with the assistance of the microscope A and the work can be restored to the operating position.

It will be understood that the mechanism above described is not limited to the production of one single and one radius for the edge of the grinding wheel but any combination of angle and radius within a range of nearly 180 is available. For example, by releasing the stud F from the secondary link D and setting one or each of the fences F in the central position, as shown diagrammatically in Figure 9, movement of the follower F along the fence or fences will result in the diamond D moving along a straight-line path so as to true a flat end surface on the grinding wheel B. Similarly, a chisel-like edge may be trued as shown in Figure 10 by moving the follower F along one of the fences F adjusted to one side of the plane of the grinding wheel so that the diamond D traverses a straight-line path from one side to the other of the grinding wheel. By successively carrying out the operations described with reference to Figures 9 and 10 two faces may be trued at a large angle to each other as shown in Figure 11. Again by preliminary adjustment somewhat similar to that described with reference to Figures '7 and 8, a grinding wheel having a curved operative edge as shown in Figure 12 may be trued, the primary axis E being displaced towards the axis of rotation of the grinding wheel B by a distance equal to half the thickness of the wheel. It will be understood that in Figure 12, as in Figures 7 and 8, the pri mary and secondary links are locked together by the spring-loaded stud F.

Figure 13 illustrates diagrammatically the manher in which the apparatus above described may be employed for truing a grinding wheel having a curved reentrant operative edge. For this purpose the primary and secondary links are again locked together by the stud F but the diamond holder D is adjusted, with the assistance of the scale A on the microscope, towards the axis of rotation of the grinding wheel B through a distance equal to the radius of the reentrant grinding surface. The bracket C is then adjusted away from the grinding wheel through a distance equal to the said radius. By swinging the primary and secondary links to and fro about the primary axis E the diamond D will move along a curved path concentric with the axis E thus truing the reentrant surface of the grinding wheel B.

It is desirable to illuminate the edge of the grinding wheel B and the diamond D for facilitating glgservation through the microscope A To this end there is mounted on a pivot G carried by the bracket C a housing G containing a lamp G and carrying a tube G containing a sleeve G longitudinally adjustable within the tube G and locked in position therein by a stud G Arranged within the sleeve G is a collimating lens G in alignment with a 45 mirror which may be formed of stainless steel to facilitate tapping of the adjusting stud shown The mirror G projects the light emerging from the lens G6 as a parallel beam through a window G and thence through the primary pivot C which is hollow for this purpose. The lamp housing G is furnished with a handle G by which the illuminating unit as a whole can be adjusted about the pivot G to bring the window G generally into alignment with the primary axis E The illuminating unit can therefore be adjusted in alignment with the primary axis for setting and finally truing and can then be swung into an inoperative position, thus reducing to a minimum the time during which the window (3: is exposed to bombardment of particles of grit which may pass through the hollow primary pivot C As shown in Figures 14 and 15 the truing unit C is adjustable transversely to the arm C along a guide H by means of a knurled head H secured to a threaded spindle H in threaded engagement with a block 1H secured to the bracket 0*. The truing unit is locked in the position of transverse adjustment by means of a stud H and ball handle H With this arrangement the illuminating system comprises a lamp housing J which can be swung about a vertical pivot by means of a handle J the construction of the illuminating unit being similar to that described with reference to Figure 5, the tubular member G extending parallel to the direction of traversing adjustment of the truing unit C by means of the knurled head H The construction shown in Figures 14 and 15 may be employed for example for truing a stepped disc wheel as shown in Figure 16. To this end the follower F is first caused to cooperate with the fence or fences F in the central position as described with reference to Figure 9 and one of the fences F is then moved over to the right and the truing unit C is traversed by means of the knurled head H to the right through a distance equal to that between the surface E and the central plane of the grinding wheel B, this adjustment being effected with the assistance of the scale A of the microscope graticule. Having trued the surface E the follower F is again restored to the central position and the truing unit C is moved upwards by the knurled head C whereupon the surface E can be trued, again in the manner described with reference to Figure 9. Figure 17 shows another form of grinding wheel which can be trued by the apparatus shown in Figures 14 and 15, the central peripheral edge portion being trued as described with reference to Figure 9 whilst the two surfaces forming each of the angles on opposite sides of the central plane of the wheel are trued in the manner described with reference to Figure 16, the truing unit C being traversed by adjustment of the head H first to one side of the central plane of the grinding wheel B and then to the other side thereof.

One corner of the operative edge of the grind ing wheel B shown in Figure 18 is rounded on a radius Whose centre E lies to one side of the central plane of the wheel B. For truing the curved portion of this surface the links D, D are locked together by the stud F and the truing unit 0 is traversed to the right as viewed in Figure 18 through a distance equal to that between the centre of curvature E and the central plane of the wheel B. The diamond D is then adjusted (with the assistance of the graticule scale A relatively to the secondary link D in a direction away from the grinding wheel B through a distance equal to the radius E". With the grinding wheel B in rotation and one fence F adjusted centrally in the slot F and the other fence F to the right of the plane of the grinding Wheel, the links D D are oscillated to and fro between the fences F and the truing unit C is adjusted towards the grinding wheel B whose curved edge is thus trued until the primary axis E coincides with the centre of curvature E this adjustment being effected with the assistance of the scale A on the microscope graticule.

The reentrant curved surface of the grinding wheel shown in Figure 19 may be trued by the apparatus shown in Figures 14 and 15 in a manner generally similar to that described with reference to Figure 13. For truing this surface, however, the truing unit C will be traversed so as to move the primary axis E to the left through a distance equal to half the thickness of the grinding Wheel and, with one fence F arranged centrally and the other to the left, the links D D locked together by the stud Ft will be oscillated between the fences and the unit C fed towards the grinding wheel until the primary axis 3 ative position before each truing operation. In 4 order to avoid the necessity for disturbing the work table and pantograph, however, a truing unit according to the invention may be arranged at the back of the machine, for example as shown in Figure 20. In this construction the truing unit C, which comprises primary and secondary links and a diamond D as above described, has its primary pivot K journalled within a housing K supported on a frame K which can be traversed along guides K by means of a knurled head K the guides K being formed in a fixed part of the supporting frame K The arcuate slot F along which the fences F above described are adjustable is formed in an integral part of the housing K the object glass of a microscope L being disposed within the primary .nivot K thus providing a practical focal length and compactness. It will be noted that with this arrangement the truing unit C is not carried upon a swinging arm as in the constructions above described but can only be moved away from the grinding wheel B by an amount as permitted by the adjustment available along the guides K With this arrangement, therefore, the truing unit C is always substantially in its operative position and truing of the grinding wheel B can be effected by merely adjusting the knurled head K so as to bring the diamond D on to the primary axis E The illuminating unit included in Figure Iii 20 comprises a lamp housing M pivoted on a fixed bracket M and furnished with a tubular part M similar to the tube G in Figure 5, the window M of the illuminating unit being brought generally into alignment with the primary axis E by turning the lamp housing M about its pivot,

a handle M being provided for this purpose, As in the construction described with reference to Figure 5, the primary pivot K is hollow so that the light beam from the window M is directed along the primary axis E towards the microscope objective.

Where intensive production, and consequent rapid wear of the grinding wheel, is liable to take place, the link mechanism and diamond may be duplicated, with the movements of the two diamonds out of phase to avoid fouling each other at the plane of the grinding wheel, a third diamond being employed for producing the radiussed edge on the wheel. One such arrangement is diagrammatically shown by way of example in Figure 21 in which there are two coaxial primary links N, P which are preferably relatively adjustable about the common primary axis E and can be locked together by a stud S Mounted to turn about secondary axes N P on the primary links N P are two secondary links N, P which respectively carry followers N, P. The followers N*, P are arranged to cooperate with fences indicated at N and P respectively, these fences being adjustable along an arcuate slot in the bracket R, this slot, which is not shown, being concentric with the primary axis E as above described with reference to the slot F The secondary links N P are provided with diamond holders N, P carrying diamonds N", P respectively. Mounted to swing about the primary pivot which is coaxial with the primary axis E is an arm S carrying a diamond S which can be drawn out away from the plane of the secondary links N P and locked in this retracted position by rotation of a knurled stud S Having retracted the diamond S the primary links N P are relatively adjusted about the primary axis E to suit the angle of the V-edge of the grinding wheel B, each fence N P being so adjusted that when the links N, P are moved so that the followers N P move along the fences N P the points of the diamonds N", P will traverse straight lines conforming to the corre-- sponding surfaces of the wheel B to be trued. Since the primary links N, P are locked together by the locking stud S they move as a unit so that while the diamond N" is moving up along the corresponding face of the grinding wheel the diamond P" is moving down along the corresponding face on the other side of the wheel, risk of the diamonds N, P fouling each other being thus obviated. Having trued the two V- faces of the grinding wheel B the two followers N, P are moved down so that the primary and secondary links of each system lie vertical, that is to say so that the diamonds N", P" lie clear of the grinding wheel B on opposite sides thereof. The diamond S is now moved up into its opera tive position and clamped therein by operation of the knurled head S Having adjusted the diamond S and the primary axis E in the manner described with reference to Figures 7 and 8, the scale A of the microscope graticule being used for this purpose, the arm S is swung to and fro about the primary axis, a stud S carried by the arm S cooperating with extensions N, P of the fences N, P to limit the swinging movement of the arm S. In this way the operative edge of the grinding wheel is trued on the required radius.

It will thus be seen that since the dressing or truing unit according to the invention is independent of the work table or support no parts have to be removed from or replaced on the grinding machine when truing is necessary, the work being either moved out of the operating position and the truing unit into the operating position or, when an arrangement such as that shown in Figure 20 is employed, remaining undisturbed. Further, since the truing unit is adapted to be mounted on the grinding machine it is always ready for use and the expenditure of time for mounting the truing mechanism manually in position on the machine before each truing operation can be commenced is obviated. The truing unit is, moreover, self-contained and does not necessitate the use of a different former for each different edge angle. Apparatus embodying the invention will remainaccurate over a long period owing to the light pressure, low rubbing velocity and adequate area of contact between the fence or fences and the follower.

Whilst two guides or fences have been described in each of the above constructions, a single fence may be employed by providing a single arcuate slot in the bracket along which the fence can be adjusted from one side to the other of the plane of rotation of the grinding wheel. Further, the truing device may lie below, above or to one side of the grinding wheel during the truing operation, the viewing microscope being horizontal when the truing device lies above or below the wheel, whereas the microscope is vertical when the truing device lies to one side of the wheel.

As will be apparent from the above description the formation of the operative edge of the grinding wheel need not necessarily be of symmetrical V-shape since by suitable modification of the formation and arrangement of the guides or fences, the operative edge of the grinding wheel may be trued to any desired shape, with two straight or curved trued faces on opposite sides of the plane of rotation or with a single trued face of any desired profile. Thus, the invention provides the further advantage that the truing unit can be employed for truing grinding wheels whose operative edges vary widely in pro. file.

Experience has shown that, especially in the case of fine-grained grinding wheels of fairly hard bond, a diamond making more than point contact will tend to glaze the wheel during the truing operation, thus impairing the cutting qualities of the wheel. A pointed diamond is therefore preferred.

What I claim as my invention and desire to secure by Letters Patent is:

1. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, and at least one straight guide on the carrier for cooperation with the follower, the distance between the secondary axis and the follower and between the secondary axis and the truing device being normally equal to the distance between the primary and secondary axes,

translational movement of the secondary link about the primary axis accompanied by pivotal movement of the secondary link about the secondary axis, as constrained by the guide engaging the follower, causing the follower to move radially with respect to the primary axis whilst the truing device moves relatively to the grinding wheel along a straight-line path.

2. In apparatus for truing grinding and abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link which also pivots about said follower, two guides on the carrier lying respectively on opposite sides of a plane containing the primary axis, and means whereby the follower can be caused to cooperate, at will, with either of the guides, movement of the truing device relatively to the grinding wheel on either side of the plane thereof being effected by moving the secondary link about the primary and secondary axes and follower as constrained by the guide in engagement with the follower on the said side of the plane of the grinding wheel.

3. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, two straight guides on the carrier lying on opposite sides respectively of a plane containing the primary axis, means for adjusting the guides concentrically with the primary axis, and means whereby the follower can be caused to cooperate, at will, with either of the guides, the distance between the secondary axis and the follower and between the secondary axis and the truing device being normally equal to the distance between the primary and secondary axes, translational movement of the secondary link about the primary axis accompanied by pivotal movement of the secondary link about the secondary axis and radial movement of the follower with respect to the primary axis as constrained by the guide in engagement with the follower on one side of the said plane, causing the truing device to move relatively to the grinding wheel along a straight line path inclined to the said plane in accordance with the position of adjustment of the said guide.

4. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, at least one guide on the carrier for cooperation with the follower, movement of the secondary link about the primary and secondary axes, as constrained by the guide engaging the follower, causing movement of the truing device relatively to the grinding wheel along a straightline path, and means for locking the primary and secondary links together so that the two links can be swung as a unit about the primary axis.

5. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, means for adjusting the truing device on the secondary link relatively to the primary and secondary axes, a follower carried by the secondary link, two straight guides on the carrier lying on opposite sides respectively of a plane containing the primary axis, means whereby the follower can be caused to cooperate, at will, with either of the guides, the distance between the secondary axis and the follower and between the secondary axis and the truing device being normally equal to the distance between the primary and secondary axes, translational movement of the secondary link about the primary axis accompanied by pivotal movement of the secondary link about the secondary axis, as constrained by that guide in engagement with the follower on either side of the said plane, causing the truing device to move relatively to the grinding wheel along a straight-line path inclined to the said plane, and means for locking the primary and secondary links together so that they can be swung as a unit about the primary axis.

6. In a unit for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a carrier adapted to be mounted on the machine, a primary link mounted to swing about a primary axis on the carrier, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, at least one straight fence on the carrier for cooperation with the follower, and a guide on the carrier concentric with the primary axis and along which guide the fence is adjustable, the distance between the secondary axis and the follower and between the secondary axis and the truing device being normally equal to the distance between the primary and secondary axes, translational movement of the secondary link about the primary axis accompanied by pivotal movement of the secondary link about the secondary axis, as constrained by the fence in engagement with the follower, causing the truing device to move relatively to the grinding wheel along a straight-line path.

7. In a u..=it for truing grinding and abrasive wheels and the like for grinding and abrading machines, in combination, a carrier adapted to be mounted on the machine, a hollow primary pivot on the carrier, a primary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, at least one fence on the carrier for cooperating with the follower, and a device which projects light through the hollow primary pivot and illuminates the working plane ILUI of cooperation between the truing device and the grinding wheel, movement of the follower along the fence radially with respect to the primary axis egusing translational movement of the secondary link about the primary axis and pivotal movement about the secondary axis, the truing device thus moving along a predetermined path relatively to the grinding wheel.

8. In a unit for truing grinding and abrasive wheels and the like, for grinding and abrading machines, in combination, a carrier adapted to be mounted on the machine, a hollow primary pivot on the carrier, a primary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, two fences on the carrier lying on opposite sides respectively of a plane containing the primary axis, a guide on the carrier concentric with the primary axis, the fences being adjustable along said concentric guide, means whereby the follower can be caused to cooperate, at will, with either of the fences, and an illuminating device which projects light through the hollow primary pivot and illuminates the working plane of cooperation between the truing device and the grinding wheel, movement of the follower along the fence radially with respect to the primary axis causing translational movement of the secondary link about the primary axis and pivotal movement about the secondary axis, the truing device thus moving along a straight-line path relatively to the grinding wheel.

9. In a unit for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a carrier adapted to be mounted on the machine, a hollow primary pivot on the carrier, a primary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, a microscope at least part of whose optical system is housed within the hollow primary pivot, and at least one fence on the carrier for cooperating with the follower, movement of the follower along the fence causing translational movement of the secondary link about the primary axis and pivotal movement about the secondary axis, the truing device thus moving along a straight-line path.

10. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, means for adjusting the carrier relatively to the support in directions transverse to the plane of the grinding wheel, a bracket mounted on the carrier, means for adjusting the bracket relatively to the carrier in directions generally parallel to the plate of the grinding wheel, a hollow primary pivot on the bracket, a truing unit carried by the bracket and comprising a primary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a secondary axis on the primary link, a truing device carried by the secondary link, a follower carried by the secondary link, at least one guide on the bracket for cooperation with the follower, a microscope mounted on the carrier, at least part of the optical system of the microscope being housed within the hollow primary pivot, and an illuminating device which projects light in alignment with the hollow primary pivot and illuminates the working plane of cooperation between the truing device and the grinding wheel, movement of the follower along the guide radially with respect to the primary axis causing the truing device to move along a straight-line path relatively to the grinding wheel.

11. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, means for effecting translational adjustment of the carrier in directions generally parallel to the plane of the grinding wheel, a hollow primary pivot on the carrier, a truing unit mounted on the carrier and comprising a pri mary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a second axis on the primary link, a follower carried by the secondary link, at least one fence mounted on the carrier for cooperation with the follower, a microscope mounted on the carrier and in optical alignment with the primary axis, and an illuminating device which projects light in alignment with the hollow primary pivot and illuminates the working plane of cooperation between the truing device and the grinding wheel, movement of the follower along the guide radially with respect to the primary axis causing the truing device to move along a straight-line path relatively to the grinding wheel.

12. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, means for effecting translational adjustment of the carrier in directions generally parallel to the plane of the grinding wheel, a hollow primary pivot on the carrier, a truing unit mounted on the carrier and comprising a primary link mounted to swing about the axis of the primary pivot, a secondary link mounted to swing about a secondary axis on the primary link, a follower carried by the secondary link, at least one fence mounted on the carrier for cooperation with the follower, a microscope forming an integral unit with the carrier, at least part of the optical system of said microscope being housed within the hollow primary pivot, and an illuminating device which projects light in alignment with the hollow primary pivot and illuminates the working plane of cooperation between the truing device and the grinding wheel, movement of the follower along the guide radially with respect to the primary axis causing the truing device to move along a. straight-line path relatively to the grinding wheel.

13. In apparatus for truing grinding or abra-' sive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising two primary links mounted to swing about a primary axis on the carrier, two secondary links mounted to swing respectively about two secondary axes on the two primary links, two truing devices carried by the secondary links respectively, two followers carried by the secondary links respectively, the secondary links also swinging about said followers as pivots, the distance between each secondary axis and the corresponding follower and between the secondary axis and the truing device being normally equal to the distance between the primary and secondary axes, and two guides mounted on the carrier for cooperation with the followers, movement, of the followers along the said guides radially with respect to the primary axis causing simultaneous movement of the truing devices, each truing device moving along a straight-line path corresponding to the surface of the grinding wheel to be trued.

14. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a support for the grinding wheel, a carrier mounted on the support, a truing unit mounted on the carrier and comprising two primary links mounted to swing about a common primary axis on the carrier, two secondary links mounted to swing respectively about two secondary axes on the two primary links, two truing devices carried by the secondary links respectively, two followers carried by the secondary links respectively, two guides mounted on the carrier for cooperation with the followers, movement of the two followers along the said guides causing translational movement of each secondary link about the primary axis and pivotal movement of each secondary link about the corresponding secondary axis, the two truing devices thus moving simultaneously, but out of phase, along straight-line paths corresponding to two faces of the grinding wheel to be trued, an intermediate member mounted to pivot about the said primary axis, a third truing device carried by the intermediate member, and means for adjusting the third truing device on the intermediate member relatively to the primary axis.

15. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, the combination with the features claimed in claim 14 of means for effecting rela tive adjustment of the two primary links about the common primary axis, and a device for looking the primary links in such position of adjustment.

16. In apparatus for truing grinding or abrasive wheels and the like for grinding and abrading machines, in combination, a supporting base, a grinding wheel mounted to rotate on said base with its operative-edge in a working plane, a carrier mounted on the said base, means for adjusting the carrier on the base towards and away from the plane of the grinding wheel, a device for locking the carrier in the desired position of adjustment, a bracket mounted on the carrier, means for adjusting the bracket on the carrier towards and away from the working plane, a truing unit mounted on the bracket and comprising a primary link mounted to swing about a primary axis on the bracket, a secondary link mounted to swing about a secondary axis on the primary link, a truing diamond carried by the secondary link, a follower carried by the secondary link, two guides on the bracket lying on opposite sides respectively of the plane of the grinding wheel, means for adjusting the guides concentrically with respect to the primary axis, means whereby the follower can be caused to cooperate, at will, with either of the guides, the distance between the secondary axis and the follower and between the secondary axis and the truing device being normally equal to the distance between the primary and the secondary axes, translational movement of the secondary link about the primary axis accompanied by pivotal movement of the secondary link about the secondary axis, as constrained by that guide in engagement with the follower on either side of the said plane, causing the truing device to move relatively to the grinding wheel along a straight-line path, means for locking the primary and secondary links together so that they can be swung as a unit about the primary axis, and means for adjusting the diamond on the secondary link relatively to the primary axis thus determining the radius of the arcuate path of movement of the diamond when the links are swung as a unit about the primary axis.

ERNEST ALBERT COOKE. 

